Internal-combustion engine



me. i926. 1,612,492

H. H. CUTLER INTERNAL COMBUSTION ENGINE Filed Feb.l 28. 1924 2 sheets-sheet 1 I M IN1/MOR Dec. 28 1926.

H. H. CUTLER INTERNAL COMEUSTILON ENGINE 2 Sheets-Sheet 2 Filed Feb. 28, 1924 A yPatented Dec. 2.8, 1926.

l UNITED STATES 1,612,492 PATENT OFFICE.

HENRY H. CUTLEB, 0F BROOKLINE, MASSACHUSETTS.

i INTERNAL-COMBUSTION ENGINE.

Application lcd February 28, 1924. `Serial No. 695,864.

My invention relates to internal combustion engines and more especially to such engines of the variable clearance type in which means are provided for varying the clearance space in unison with the movement of the power piston for securing more complete scavenging of the cylinder after every explosion.

The present invention is a development of that disclosed in my application Serial No. 445,690, filed February 17, 1921, of which this application is a continuation.

' Variable clearance engines of the type shown in my Letters Patent 1,301,658 issued April 22, 1919, on an application tiled May 18, 1917, are subject to certain limitations due chiefly to the demonstrated impossibility of preventing j leakage around the piston rings of the supplemental piston.

The principal object of the invention 1s to provide a supplemental Apiston so constructed and arranged as to form with the cylinder head an Iairtight chamber, of suoli volume that the air compressed therein by Said supplemental piston will attain' a pressure equal approximately to that exerted on the combustion chamber face of said supplemental piston during the power and compression strokes and thereby form a pneumatic cushion limiting the outward movement of 1 said supplemental piston. rlliis object I attain by ,the use ofa ringless supplemental piston so constructed and arranged that the contacting portions of the cylinder and supplemental piston are maintained at substantially the same temperature thereby permitting of a substantially gastight fit of said supplemental piston in said cylinder without the'frictional loss due to the use of piston rings.

One embodiment of m invention whereby the foregoing object is o tained consists of a hollow supp emental piston having its cylindrical wall arranged within and closely {itting into the space between the interior wall of the c linder and the reduced end portion of a hol ow plug extending into the cylinder and closing end thereof, said hollow plug communicating with the water-cooling system so that the cylindrical Wall of the supplemental piston is cooled on the inside by the water inside of said plug, and on the outside bythe water in the jacket of the cylinder.

Other objects of my invention and novel features of construction are'hereinafter set forth, and the constructions whereby said objects are realized are particularly pointed out in the appended claims.

My inventionis the result of experimental work and experience derived largely from constructing and operating the internal combustion engine described in my Letters Patent No. 1,301,658, dated May 18, 1917, as well as other engines similar to the types illustrated herewith.

` The main object of my present invention is the same as that set forth in the above mentioned patent, namely, to provide means for automatically efecting complete mechanical scavenging of the cylinder at the end of every exhaust stroke, and to avoid the undesirable features which the testing of this earlier type of engine developed.

These undesirable features were, first, ex-

cessive leakage by the scavenging pistons of both oil and the working mixture, plainly visible in this type of engine, 'and giving an ocular demonstration of the large amount of leakage that takes place by the power "pistons of all internal combustion engines,

no matter how well constructed. Second, there was also developed a large additional loss due to friction of the piston rings of the scavenging pistons, inertia losses in sto ping and accelerating the comparative y heavy scavenging pistons, connecting rods, etc., and the still further friction losses of all the other extra movin arts. Third, the net result was only a s 'g t increase in economy and Aavailable power.

My present invention aims to overcome all of the above mentioned undesirable features, as well as to simplify'and cheapen the mechanical construction.

' The accompanying drawings show vtwo slightly different embodiments of my invention.

Figure 1 is a longitudinal vertical section of a four cylinder-internal combustion engine embodying my invention, and showing the relative position of the moving parts on 4completion of the compression stroke in cylinder numbered 10 in said figure.

Fig. 2 is a longitudinal vertical section taken through the middle of one of the engine cylinders at right angles to Fig. 1 showing the relative position of the moving parts at the beginning of the power stroke.

Fig. 3 is a section similar to Fig. 2 illustrating a modification of my invention, and showing'the relative position of the `moving parts at the end of the exhaust stroke. n piacey of the usual demountable head, I provide a single unit head consisting of the casting 17 secured by bolts 17 (Fi l), to the top of the cylinder block 14 in t e usual manner. In the casting 17 cylinders18, 19, 20 and 21 are formed and constitute extensions of referably smaller diameter than the cylin ers 10, 11, 12 and 13, respectively, of the main engine block 14. It will be understood that such cylinder extensions ma be formed in any other suitablemanner suc as casting them intgral with the en.- gine cylinders.

At the extremeend of each cylinder extension is a fixed head or plug 22, 23, 24 and 25, respectively, each head being hollow and connected with the water jacket by passageways 26, 26. It is essential that there shall be a gas and water-tight joint between the fixed head and the wall of the cylinder in which it is placed. While such gas-tight joints may be eected in-various ways, I prefer to shrink the cylinder on to the head by turning the latter a few thousandths of an inch larger in diameter, at the top, than the bore of the cylinder, then heating the entire cylinder casting and placing the heads therein cold, so that when the cylinder casting cools, the heads will be firmly gripped. Thisphasbeen found in practice to lbe sui, cient not only to make a perfect water and gas-tight joint, but also to stand the prlessure of the exploded gases under wor `ng conditions., l

Arranged for longitudinal movement in each cylinder is a movable member 28, 29, 3()

and 31 res ectively, the portion or volume of each cylinder between-the power pistons 32, 33, 34 and35 and 'said movable members 28, 29, Y30 and 31, respectively, forming compression chambers 75, and means are vprovided for automatically controlling the position of said movable members 28, 29,

-30 and 31 to vary the volume of said compression chamber 7 5 in accordance with the variation of the load on the engine. The position of said movable members 28, 29, 30 and 31 is controlled automatically and resiliently for the purposes above specified, and after each explosion of the working mixture the position of said movable members 28, 29, 30 and 31 is changed] automatically' in order'to effect the complete mechanical scavenging of the cylinders, such control of position bein eected by combined spring and pneumatlc means.

. 'In Fig. 1 dash-pot pistons 36, 37, 38 and 39 are shown arranged to work-ina cylinder formed in the fixed cylinder heads 22, 23, 24 and 25, and rods 40, 41, 42 and 43 passing through the said fixed heads 22, 23, 24 and 25 serve to connect each dash-pot piston with its respective scavenging piston. It is essential that the said piston rods 40, 41, 42 and 43 should make a practically gas-tight joint where they pass through'the fixed `heads 22, 23, 24, and 25, and at the same time'have no 'tendency to cramp the scavenging pistons in case said piston rods were not fastened absolutelygin-the center of they said scavenging piston. I provide for this contingency by attaching the piston rods to their respective scavenging pistons in such a way as to allow of a very slight lateral movement at the joint between the two, but without allowing any vertical play.

This feature is accomplished by means of the heads 40', 41', 42 and 43 formed on the 'end of each piston rod, which heads are inserted in a hole turned in -the scavenging piston and then covered with washers 40,

41h, 42", 43L1 riveted as shown to the scavengj ing pistons so as to allow of no vertical lost motion, but avslight amount of lateral lost motion or play. The ends of said piston rods 40", 41', 42 and 43 are referably threaded and screwedinto the l ash-pot pistons 36, 37, 38 and 39 and then-fastened with taper pins or set screws.l

Attached rigidly to each one of the dashpot pistons 36, 37, 38 and 39 are strong spiral springs 45", 45', 45e, and 45d, respectively, the other'end of said springs'beingv fastened" in like manner to collars 46a, 46".

46c ando46l. The preferred'methods of at; taching said springs to said dash-pot pistons and collars. is by means of electric arc welding. It is evident that a'spring constructed in this manner may be used either as a comression or a tension spring. ars are threaded inside and held. to a channel iron cross bar 52 by means of bolts 53,

The scavenging piston 28 is shown lifted b the compresslon 1n cylinder number 10, Big. 1, thereby compressing the spring 45,

and in Fig. 2 the. scavenging piston 28 has compressed the spring 45 still further, due to the increased pressure of the explosion oi the working mixture at the beginning' oi the power stroke.

The scavenging pistons 28, 29, 30 and 31 are lshown in the drawings with extremely thin walls and no piston rings.' These walls slide freely between the walls of the cylinders 18, 19, 20 and 21, and the fixed heads 22, 23, 24 and 25. And since both the outside of said cylinders and the inside of said fixed heads are kept filled with the water supplied by the water cooling system of the engine, the said scavenging pistons 28, 29, 30 and 31 are subjected both inside and outside to the cooling effect of the water. This means that the top part of the walls of said scavenging pistons will be kept at approximately the same temperature as that of said,

loo All the collstroke, piston 34 at the end of its power stroke, and stroke.4

When the power piston 32 was moving inwardly (upwardly) during its compression stroke, and before reaching the position shown in Fig. 1, it was gradually compressing the working mixture in the comprespiston 35 at the end of its exhaust sion chamber 75, and the pressure insaid chamber 75 was gradually moving the scavenging piston 28 upward against the combined pressure of the powerful spring 45 and the air compressed in the amber 76 between the inner face of thejs'cavenging piston 28 and the fixed head 22.

The distance which the scavenging piston is moved inwardly during the compression stroke varies with the amount of working mixture which has been admitted to the cylinder during the intake stroke, deter mined by the amount of opening of the throttle valve on the carburetor. It will thus be seen that the position of the scav enging piston with respect to the power piston is automatically controlled resiliently .and will vary the volume of the compression chamber in accordance with they variation of the load on the engine.

It should not be, understood however that this action maintains the degree of compression approximately constant under variable load, as it is manifest that the more the springs 45 are compressed, as well as the air in the chambers 76, the greater must be the pressure in the chambers 75. In order to maintain a fairly constant compression undervariable load,`it is manifest that a constant pressure upon the scavenging pistons would have to be maintained at any and all positions to which these were moved.

The construction shown in the accompanying drawings'does not permit therefore of maintaining a constant degree of compression ,under a variable load, and such a requirement necessitates a very different form of construction; .y

The working mixture having beenv compressed in the chamber 75, it is then fired by means of the spark plug 66 and the scavenging piston 28 is forced up nearer to the fixed head 22, as shown in Fig. 2. Inasmuch as the explosion of such a pure compressed mixture may result in a pressure of three or four hundred pounds per square inch, it lwill be obvious that no spring could be made to withstand this relatively great pressure and still be sufciently elastic to return the scavenging piston 28 in time to keep step with an engine running at onel or two thousand revolutions a minute. All springs possess a very appreciable time lag, the larger and more powerful thespring, the slower it can vibrate. I therefore design my spring 45 so as to have sufficient strength to resist .the pressure of the compression of the working mixture and depend upon the pneumatic cushion of air in the chamber 76 to absorb or resist the pressure of the werking mixture at the time ofthe explosion and thus prevent To effect this result it is essential that said chamber 76 be absolutel airtight, and that the juxtaposed faces o the head and piston shall be exactly the same shape, so :that there will be no projection on the one Y*not matched by an indentation on the other.

The air in the scavengingpiston chamberj can then be raised to an enormous pressure and the scavenging piston can never be forced against the head which obviously would be fatal to operation.

The air in the chamber 7 6 cannot leak by the scavenging piston, 28 into the compression chamber 7 5, because the pressure of the burning gases inl the chamber is initially much greater than the pressureA of air in the chamber 7 6,' inasmuch as the pressure in the compression orcombustion chamber 7 5l acts to partly compress the spring 45, as well as to partly compress the air in the chamber 76. Therefore any leakage past the scavenging piston- 28 would be from the combustion chamber 75 and would simplysupply 4ad- 1 the scavenging piston from striking the tixed ditionalV air or gas to assist incushioning the scavenging piston 28 and thus prevent its striking the fixed head 22.

That there is no perceptible leakage from the chamber 76 by the piston rod 40 into the dash-pot chamber has been fully demonstrated inV practice.

Now as soon as the charge'h-asbeen fired, the power piston 32 moves outwardly on its power stroke, and the pressure of the burning gases between the power piston and the scavenging piston 28 falls oli'. This will allow the pressure back of the scavenging piston to move the same downwardly and inwardly so -as to maintain the total pressure approximately equal on both sides of the scavenging piston. This process goes on,until thel exhaust valve starts to open, which generally occurs when the power piston has completed about seven-eighths ol its power stroke. Now since the ressure of the burning gases, at the time o the exhaust valve starts to open, is almost invariably considerably less than the corresponding pressure of compression, 1t 1s evident that the scavenging piston 28 willv have moved down (inwardly) to a position considerably lower than it occupied at the end the air in the chamber 76, is now freeto.

push the scavenging piston down s o as to quite quickly reach its .normal position as indicated by the scavenging pistons 29, 30 and 31. 'These pistons, together with their rods, dash-pot plstons, etc., will thus acquire more or less momentum causing them to move down somewhat lower than their normal position. This action however willstretch the springs 45, as well as compress the air under the dash-pot pistons 46 so that the scavenging pistons will be promptly brought back to normal position in a smootl and noiseless manner.

Since the springs 45 are made very strong, the pressure of a pound or two back pressure of the exhaust gases will not be suiicient to cause any appreciable upward movement of the scavenging pistons, so that at the end of the exhaust stroke the power pistonl will approach very close to the scavenging piston and thus mechanically expel all of the spent exhaust gases except the small amount contained in the valve chamber 79 (Fig. 2), which in the drawings submitted amounts to but 61/2% of the total contents of lthe engine cylinder at the end of the intake4 stroke. The percentage of adulteration in the standard non-scavenging engine of this particular make figures about 28%. l

-It is obvious that a compressed mixture of hydro-carbon gas, adulterated with 61,5% of dead inert gases will burnwith far greater eiiiciency and resulting pressure than one adulterated with 28% ofI dead gas, which gain in efficiency and available power isthe chief advantage of my invention. j

It is furthermore obvious that, as previously pointed out, unless the air chamber 76 is so constructed that the compressed air within it cannot escape,the device becomes inoperative, and thatI in order to obtain such an air-tight chamber, it isessential to employ a carefully fitted piston rod of comparatively small diameter and considerable length, and that any attempt .to hold back the compressed air by means of a piston and rings exposed over its entire diameter to the outside atmosphere cannot possibly result in obtaining an air-tight chamber that would 65 prevent the scavenging piston from striking 4 the exhaust during the latter part ofthe.

exhaust stroke.

In order to distinguish the spring 45 from the spring'45, the spring 45 is shown drawn in single lines and not in section.

The chamber 76', Fig. 3, is shown somewhat smaller in volume than chamber 76, Fig. 1, otherwise the compression stroke oi the engine could not compress'the working mixture to the same amount as there is pratically little to resist the upward movement of the plunger 28 except the compression ot' the air in the chamber 7 6.

At the end of the compression stroke-the lplunger 28 will have moved up until the pressure. on both sides of the scavenging psto-n 28 is practically the same, and then when the explosionoccurs will move up a very little closer tothe fixed head 22 than was the case with scavenging piston 22, Fig. 2.

l'he construction shown in Fig. 3 possesses the marked advantage over that shown in Fig. 2 in that the scavenging piston 28 becomes almost practically incapable of leaking in practice to any appreciable amount for the reason that the pressure ol' thc air insidethe scavenging piston 28 at all times almost exactly balances the pres-- sure of the workingmixture outside the said piston, and at times this balance of pressure is identical as can be mathematically demonstrated as follows. As a practical ldemonstration 'of this truth we will apply my invention to the engine most universally used in this country, of which there are more in use than all other makes combined.

The drawings submitted show the following vdimensions:-Diameter lof scavenging pistons 31/2=9.62 sq. in. area, diameter of piston rods gzl sq. in. area, strength of spring 45 at 2 lbs. per square inchz-.9-62 )(2:1924.- pounds, strength of spring 45 when compressed 1/2 inch=1924 pounds,l

Now assume that at the time of exploding the working mixture a gauge pressure is realized of 300 pounds per rsquare inch. The scavenging piston 28 will then be forced up to within about fg of the xed head 22, thereby compressing the spring 1116 roo llO

inches more; therefore total lcompression of pringL-l/Z-l-l-iJF-:lf Spring 45 will en exert a total pressure on the scavenging-piston asi of X-160.125 pounds.

v Let wequ'al pressure of air inside the scavit must be admitted that as compared withthepower pistons, my scavenging piston 28".

enging pistonv 28 then w(9.62-.15)+48.1= 9.62 X 300. l 9.47m 2886 48.1 2825.875

pounds,` therefore :1;:2984 pounds, a differ-' ence in pressure of but 1.6 pounds 'between the two sides of the scaven 'ng piston..

Using the same dataY an assuming that an explosive pressure''wasV realized of 400' pounds tothe square inch, the resulting pressure (w) inside lthe scavenging piston would be about 399.98 ounds. If onlyr 200 pounds was obtained ai) would equal about 197 pounds and at 60 pounds compression equals about 55.7 pounds. v

When it is consideredv entire pressure of the explosion with no opposing pressure in. thev crank case, that power pistons cannot -be made to fit closely in the cylinders, that the friction of4 the piston rings and thrust oi?v the connectin rods soon wears the cylinders out of 'roun is from a practical and commerclal standpoint absolutely leakless, andjthaty conse; quently none of the-.working mixture is lost. byleaking by the scavenging-piston durlng the compression stroke,`and .also that the friction and wear of my scavenging piston` is negligible.

, Since the air in the chamber 761 will quickly become hot and Athereby tend to increase in pressure, I have provided the small airvent hole 77 which connects with the outside air by means of the hole 7 8A drilled from the upper end of the piston rod 4U to meet said hole 77. This construction prevents any accumulation of air or. gas in the chamber 76.

The chief, advantage of the construction shown in Figs. 1 and 2 over that shown in- Fig. 3 consists in the greater amount of resilient recoiljpossible at the time of theA explosion. This` extra movement'. pf the scavenging piston by quickly enlarging the volume of the combustion chamber` at the instant the working mixture is fired, seryes to absorb the Waveofhigh vpressure which occurs at this time. This property of the working mixture. now in common use is an important determining factor. 1n llmiting the amount of compression an engine can` stand without knocking, and forces designers v to use a lower ,compression atthe expense..

of both` economyof fuel and greater available power. 1

Having thus described two illustrative embodimeiits'A of my invention without however hat the power-piss Vtons of the vengine have` to withstand the limiting the same thereto, what I claim and desire to secure by Letters Patent'isz- 1. In an internal combustion engine the combination with a cylinder and power piston of a'supplemental piston located between said powerpiston and the head ofsaid cylindeigsaid sub-piston being constructed and arranged to-form with said head ank air-tight chamber of such volume that the air compressed therein bysaid supplemental piston during the power and compression vstrokes. will constitute a pneumatic cushion'limiting the outward movement of said supplemental tonof a supplemental piston located between said power piston and the fixedv head of said cylinder,v said supplemental piston being lconstructed and arrangedto form with said head v.anair-tight chambergof such volume that thelair compressed therein by saidsupplemental piston during the power and vcoinpression strokes will constitute'apneuma'tic cushion limiting 'the "outward movement of` said supplemental piston,-and al combined compression,- and tension spring rigidly attached at one endto said sup lemental piston and also rigidly attache at 'the' other end to a stationary part of said enginer said spring being thereby adapted to `resist the"- movement in either direction :of said supiA ple'mental piston and thus capable of returning the same toits normal position, after v being moved fromsaid normal position in either directionbythe action of said engine.

tween said power piston and the head of said cylinderand forming with said head an'airtight air chamber, a piston rod connected with said sub-piston and reciprocable in ya relatively long bearing inthe saidfhead, and "a combined com ression and, tension spring rigidlyattache .to'said pistonrod at one end and to a ri 'id supportfat the other Aend for holding said sub-piston in a normal fixed position and resisting the movement of the saine in either direction.-

3. In an internal combustion engine the combination-with a cylinder `and its power v piston of a supplemental piston located be-'- '4. In an internal combustion engine the :combination with a cylinder and power piston, of a supplemental piston located between said power piston and the head of said c lindeigsaid supplemental-piston being vso shaped as to fit closely over a projection of the head of said cylinder so as -to form an air-tight chamber wherein a pneumatic cushion for said supplemental piston vis iso spectively, so as to resist the movement of said supplemental piston in either direction, and automatically and silently return 'the same to its normal position during the intake and exhaust strokes of the engine.

5. In an internal combustion engine the combination with a cylinder and power piston therein, of a supplemental piston subject to 'the pressure of the working mixeture of said cylinder, said supplemental piston being located between said power piston yand the head of said cylinder and. constructed and arranged to form with said head an airtight chamber wherein a pneu.- matic cushion is formed by the outward movement oi said supplemental piston to prevent the latter :from striking against said head during the ower and compression strokes, and a spring attached at its two ends to said supplemental piston and said mienne head respectively and having suiiicient strength only` to hold said supplemental piston'in normal position, when not subjected to the pressure of the working mix- 'ture in said cylinder during the compression or working strokes of the engine.

6. In an internal combustion engine the tioned and arranged that at all points in the cycle the gaseous pressure exerted on the outward surface of said supplemental piston is substantially equal to the pressure exerted by the working mixture on the inward surface thereof. y

In testimony whereof, I have hereunto subscribed my name this 26th day of February, 1924.

. HENRY H. CUTLER. 

